Processes of producing uranium trioxide



United States of America as represented by the United States Atomic Energy Commission A lication a es; 1944*, Serial-No; 537,516

8 Claims. c1. 23-145 This invention relates to the manufacture of uranium trioxide, especially its preparation ma state whereby it reacts rapidly with carbon tetrachloride. More. particularly it appertains to the employment er ammoniunihydroxide in the production of the uranium tetraoxide which is subsequently converted to uranium trioxide.

A need for uranium tetra, pent'a and hexachloride in large quantities exists in industry. Carbon tetrachloride reacts with uranium trioxide to form these several chlorides and both source materials are readily obtained at reasonable costs. Unfortunately the yields from this reaction have been so low that the process has been a mere laboratory curiosity. Various expedie'nts, siich as (.1) preparation of the trioxide by different chemical processes, for example, that of Rosenheim and'Daehr (ZeitL Anorg. Chemie, 1929, vol. 181, page 1l7s])',,and (2) screening and' employment of t'rioxide of'difier'entdegrees of fineness, have not given significant differences in results.

This invention has for an ohjeet the preparation of uranium trioxide ina state enabling, it. to react satisfactorily with Carbon tetrachloride. Other objects are to prepare uranium trioxide and uranium. tetraoxide. Further objects are to prepare uraniun'i tetrao'xide from a uranium compound in such a state thatit can be con verted to a very reactive form of uranium. trio'xide and to treat uranium tetraoxidewith ammonium hydroxide. Still further objects are to'prepare and/or wash uranium tetraoxide in the presence of ammonium hydroxide solutions and control the cheiriieal and7or physical state of uranium tetraoxide byslurr'yiiigwith aqueous ammonium hydroxide. A general advance, in the art and dther objects which will'appearl hereinafter are also contemplated.

It has now been found that treatment of uranium tetraoxide slurries or suspensions with. aqueous ammonium hydroxide, gives a materialwhich upon heating yields a uranium trioxide' capable; of rapid and" complete reaction with carbon tetrachloride.

How the foregoing objects and related ends are accomplished will be apparent from the following exposition in which are disclosed the principle, the organization and divers embodiments of the invention, including the best mode contemplated for carrying out the same. Parts are given by weight throughout the written description, and it is amplified by the accompanying drawing which shows a flow diagram of the preferred operations.

Example I Enough water to make a thin paste was added to 1000 parts of uranium dioxide in a glass lined vessel and the resultant stirred until uniform. Then 1410 parts of nitric acid (69% HNO3) were added cautiously. The fumes given off, being pernicious and noxious were drawn away as fast as formed. The reaction mass was boiled until all nitrogen dioxide (N02) fumes had been expelled.

Crystals of uranyl nitrate, probably uranyl nitrate hexahydrate UOz(NO3)2-6HzO, usually form in the boiling liquid and'the boiling may, if desired, be stopped when their presence is noted.

nited States Patent T fatented Nov. 8, 1955 tetraoxide, probably the dihydrate UO4-2H2O, is a smooth yellowish white precipitate or suspension similar inappearance and consistency to mayonnaise.

The preparation was then thinned gradually by adding four times its volume of ammonia water. The ammonia solution used was made by combining concentrated NH4OH (28% by weight), and H20 in the ratio 1:19 by volume. The preparation was kept uniform throughout, particularly during the initial doubling of its volume, by efiicie'nt stirring. If all the' ammonia water is added at once it is difficult' to get eflicient stirring.

The resultant product was then diluted with one and one-half times'itsv'olume of water, stirred touniformity and allowed to settle. After three hours (usually' three to four hours is adequate settling. time) the supernatant liquid was siphoned off and an equal volume of ammonia water (20cc. concentrated NH4OI-I, per liter of water) added. The resultant was stirred to mix thoroughly, allowed to standthree hours and the" clear liquid again siphoned ofi. This last washing operation was repeated and the sediment filtered on a Biichner type funnel.

Contin'ued washing causes the precipitate tosettle'more and more" slowly; This causes some" delay in filterihg but does no harm to the chemical features of the procedure or reactivity of the product. Experience has shown that a filter cake about oneinch thick'is desirable for the subsequent manipulation's' and handling;

The filter cake of uranium tetraoxide was dried i n porcelain pans or trays" for 12 to 16' hoursat to 80 C, producing possibly the monohydrate UOi-HzO. The dried cakes were crushed to powder in a mortar type pulverizer. v I

If the drying has'not'b'e'en done correctly it is diificult to get a smooth powder at this stage. Drying too long gives a: cakewhich is'too' hard. Insuflicient drying gives a cakewhich packs in grindin'g; V

The drypowder was placedin a glass lined' container, connected to a vacuum ump and raised to and maintained at 200 C. untilmostof the water was driven off. The temperature was then gradually raised to 325 C and there maint ined for one to two hours and allowed to cool, whereby uraniumgt'r'ioxide in the from of a very'reactive'redpo'wderresulted. This UOs' powder was transferred to a dry storage vessel as rapidly as possible to A thin paste was made by adding water to 1000 parts of uranium dioxide and stirring. Then 1946 parts of nitric acid (50% HNOa) were added slowly. The fumes given off were drawn away rapidly while boiling the reaction mass to expel all nitrogen dioxide (N02) fumes.

The preparation was diluted until the mixture contained 660 parts of uranyl nitrate [UO2(NO3)2] per liter and the temperature of the liquid brought to C. whereupon 908 parts of 30% hydrogen peroxide were added.

The preparation was then thinned slowly by adding four times its volume of concentrated ammonium hydroxide (28%) diluted with 19 times its volume of water. The preparation was kept uniform throughout by eflicient stirring. I

The resultant product was then diluted with an equal volume of water, stirred to uniformity and allowed to settle. After four hours the supernatant liquid was siphoned off and an equal volume of ammonia water cc. concentrated NH4OH per liter of water) added. The

resultant was stirred thoroughly, allowed to stand approximately three hours and the clear liquid again siphoned off. The washing operation was repeated and the sediment filtered on a Biichner type funnel.

The filter cake was dried in porcelain pans or trays for 15 hours at 75 C. The dried product was crushed to powder.

The dry powder was placed in a glass container under vacuum and raised to and maintained at 200 C. until most of the water was driven off. The temperature was then slowly raised to 325 C. and there maintained for one to two hours and allowed to cool, resulting in a highly reactive form of U03.

Example III Enough water to make a thin paste was added, with agitation, to 1000 parts of uranium dioxide in a glass vessel. Then 1622 parts of nitricacid (60% HNOs) were added. The reaction mass was boiled to expel all nitrogen dioxide (N02) and the fumes were drawn away as fast as formed.

The preparation was then diluted until the mixture contained 660 parts of uranyl nitrate [UO2(NO3)2] per liter and the temperature of the liquid to 78 C. whereupon 908 parts of hydrogen peroxide were added.

The preparation was then thinned by adding four times its volume of ammonia Water. The preparation was kept uniform throughout the addition by agitation. When all a the ammonia water is added quickly it is difficult to get good stirring.

The resultant product was then diluted with one and one-quarter times its volume of water, stirred to uniformity and allowed to settle. After three and one-half hours the supernatant liquid was siphoned off and an equal volume of ammonia water (20 cc. concentrated NH4OH per liter of water) added. The resultant was mixed thoroughly, allowed to stand about three hours and the clear liquid again siphoned off. The washing operation was repeated and the product filtered on a Buchner type funnel.

The filter cake was dried in porcelain pans or trays for 16 hours at 70 C. The dried material was powdered.

The dry powder was placed in a glass ceramic lined container, placed under a vacuum and raised to and maintained at 200 C. until most of the water was driven off. The temperature was then raised to 325 C. and there maintained for one to two hours and allowed to cool, resulting in the formation of active U03.

In the manufacture of the uranium nitrate, compounds other than uranium dioxide, for example, uranium trioxide (U03) and uranous-uranic oxide (U308) may be used. Also, instead of converting the raw material to uranyl nitrate in the process described this material may be converted to the acetate, chloride, sulfate, etc. if desired, which material is then subjected to the hydrogen peroxide treatment prescribed.

The flow diagram in the single figure of the drawing illustrates the general features of the improved process and various modifications and equivalents will be obvious to those skilled in the art. There is no need to lengthen this specification by including such material.

A satisfactory explanation for the tremendous increase in reactivity of the uranium trioxide as a result of treating the uranium tetraoxide with ammonia water is not at present available.

Probably many apparently widely different embodiments of this invention may be made without departing from the principle, breadth and spirit thereof and it is to be understood therefore that this invention is not limited to the specific embodiments thereof except as encompassed in the claims.

What is claimed is:

l. The process which comprises washing uranium tetraoxide with ammonium hydroxide, separating the uranium tetraoxide and heating to convert it to uranium trioxide.

2. In the manufacture of uranium trioxide the steps of treating an aqueous suspension of uranium tetraoxide with aqueous ammonium hydroxide and thereafter heating the uranium tetraoxide to form uranium trioxide.

3. Process of manufacturing highly reactive uranium trioxide comprising washing uranium tetraoxide with dilute ammonium hydroxide, filtering, drying at to C. for 12 to 16 hours, powdering, dehydrating at 200 C. and heating at 325 C. for l to 2 hours to form uranium trioxide.

4. Method of manufacturing uranium trioxide capable of rapid reaction with carbon tetrachloride which comprises slurrying uranium tetraoxide with ammonia water, decanting, washing with ammonia water, separating the solid uranium tetraoxide and heating to convert to uranium trioxide.

5. In the manufacture of uranium trioxide the steps of treating uranium tetraoxide with aqueous solutions of ammonium hydroxide of progressively decreasing strength, and thereafter heating the uranium tetraoxide to form uranium trioxide.

6. In the manufacture of uranium trioxide the steps of successively treating uranium tetraoxide with a plurality of dilute aqueous solutions of ammonium hydroxide, and thereafter heating the uranium tetraoxide to form uranium trioxide.

7. The process comprising washing uranium tetraoxide with ammonium hydroxide.

8. The process comprising successively treating freshly precipitated uranium tetraoxide with a plurality of aqueous solutions of ammonium hydroxide.

References Cited in the file of this patent Mellor: Inorganic and Theoretical Chemistry, vol. 12, pages 55, 69 and 70. Longmans, London (1932). 

1. THE PROCESS WHICH COMPRISES WASHING URANIUM TETRAOXIDE WITH AMMONIUM HYDROXIDE, SEPARATING THE URANIUM TETRAOXIDE AND HEATING TO CONVERT IT TO URANIUM TRIOXIDE,
 7. THE PROCESS COMPRISING WASHING URANIUM TETRAOXIDE WITH AMMONIUM HYDROXIDE. 